Ingestion of sodium plus water improves cardiovascular function and performance during dehydrating cycling in the heat

We studied if salt and water ingestion alleviates the physiological strain caused by dehydrating exercise in the heat. Ten trained male cyclists ( : 60 ± 7 mL/kg/min) completed three randomized trials in a hot‐dry environment (33 °C, 30% rh, 2.5 m/s airflow). Ninety minutes before the exercise, participants ingested 10 mL of water/kg body mass either alone (CON trial) or with salt to result in concentrations of 82 or 164 mM Na⁺ (ModNa⁺ or HighNa⁺ trial, respectively). Then, participants cycled at 63% of for 120 min immediately followed by a time‐trial. After 120 min of exercise, the reduction in plasma volume was lessened with ModNa⁺ and HighNa⁺ trials (?11.9 ± 2.1 and ?9.8 ± 4.2%) in comparison with CON (?16.4 ± 3.2%; P < 0.05). However, heat accumulation or dissipation (forearm skin blood flow and sweat rate) were not improved by salt ingestion. In contrast, both salt trials maintained cardiac output (～1.3 ± 1.4 L/min; P < 0.05) and stroke volume (～10 ± 11 mL/beat; P < 0.05) above CON after 120 min of exercise. Furthermore, the salt trials equally improved time‐trial performance by 7.4% above CON (～289 ± 42 vs 269 ± 50 W, respectively; P < 0.05). Our data suggest that pre‐exercise ingestion of salt plus water maintains higher plasma volume during dehydrating exercise in the heat without thermoregulatory effects. However, it maintains cardiovascular function and improves cycling performance.     

Influence of 4 weeks of bovine colostrum supplementation on neutrophil and mucosal immune responses to prolonged cycling

Bovine colostrum (COL) has been advocated as a nutritional countermeasure to exercise‐induced immune dysfunction. The aims of this study were to identify the effects of 4 weeks of COL supplementation on neutrophil responses and mucosal immunity following prolonged exercise. In a randomized double‐blind, parallel group design, participants [age 28 ± 8 years; body mass 79 ± 7 kg; height 182 ± 6 cm; maximal oxygen uptake () 55 ± 9 mL/kg/min] were assigned to 20 g per day of COL (n = 10) or an isoenergetic/isomacronutrient placebo (PLA; n = 10) for 4 weeks. Venous blood and unstimulated saliva samples were obtained before and after 2.5 h of cycling at 15% Δ (～55–60% ). A significantly greater formyl‐methionyl‐leucyl phenylalanine‐stimulated oxidative burst was observed in the COL group compared with PLA group (P < 0.05) and a trend toward a time × group interaction (P = 0.06). However, there was no effect of COL on leukocyte trafficking, phorbol‐12‐myristate‐13‐acetate‐stimulated oxidative burst, bacterial‐stimulated neutrophil degranulation, salivary secretory IgA, lactoferrin or lysozyme (P > 0.05). These findings provide further evidence of the beneficial effects of COL on receptor‐mediated stimulation of neutrophil oxidative burst in a model of exercise‐induced immune dysfunction.     

Effects of montmorency tart cherry (L. Prunus Cerasus) consumption on nitric oxide biomarkers and exercise performance

The purpose of this study was to investigate the effects of Montmorency tart cherry juice (MC ) on nitric oxide (NO ) biomarkers, vascular function, and exercise performance. In a randomized, double‐blind, placebo (PLA )‐controlled, crossover study, 10 trained cyclists (mean ± SD ; O_2peak 59.0 ± 7.0 mL/kg/min) acutely ingested 30 mL of either MC or PLA following dietary restrictions of polyphenol‐rich compounds and completed 6‐minutes moderate‐ and severe‐intensity cycling bouts 1.5 hour post‐ingestion on 2 occasions for each experimental condition. The severe‐intensity cycling test was continued to exhaustion on 1 occasion and immediately followed by a 60‐seconds all‐out sprint on the other occasion. Blood pressure, pulse wave measures, tissue oxygenation index, and plasma nitrite concentration were assessed pre‐ and 1.5 hour post‐ingestion. Time to exhaustion was not different between conditions (P  >  .05), but peak power over the first 20 seconds (363 ± 42 vs 330 ± 26 W) and total work completed during the 60‐seconds all‐out sprint (21 ± 3 vs 19 ± 3 kJ ) were 10% higher in the MC trial compared to the PLA trial (P  <  .05). Systolic blood pressure was 5 ± 2 mm Hg lower 1.5 hour post‐MC supplementation compared to PLA supplementation (P  <  .05). There were no differences in pulse wave measures, plasma nitrite concentration, or tissue oxygenation between the MC and PLA trials (P  >  .05). These results suggest that acute supplementation with MC can lower blood pressure and improve some aspects of exercise performance, specifically end‐sprint performance, in trained cyclists.     

Cardiorespiratory fitness and heart rate recovery in obese premenopausal women

Post‐exercise heart rate recovery (HRR) has been proposed as a measure of cardiac autonomic dysfunction in apparently healthy adults. We aimed to determine the effects of a lifestyle intervention on HRR among clinically obese premenopausal women. A randomized controlled trial was conducted to investigate the effects of a 3‐month non‐dieting lifestyle intervention program on cardiorespiratory fitness (CRF) and HRR among healthy clinically obese premenopausal women. Thirty‐one were randomly assigned to 3‐month intensive lifestyle intervention and 31 served as controls. Sixty‐one participants performed a maximal treadmill walking test with metabolic gas exchange. Baseline anthropometric measures were closely related to HRR at 1 min, which may indicate reduced parasympathetic reactivation. Post‐exercise HRR at 60 s (HRR60) increased from 21.3 ± 6.2 to 27.8 ± 10.2 bpm in the intervention group compared with a smaller reduction (26.8 ± 12.3 to 24.5 ± 9.9 bpm) in controls (test for interaction P = 0.0001). HRR120 showed a significant effect of time (P = 0.0002) with no significant interaction with lifestyle intervention. A significant increase in was evident in the lifestyle group (21.6 to 23.6 mL/kg/min) compared with a modest reduction in the controls (22.6 to 21.6 mL/kg/min; test for interaction, P = 0.001). Clinically obese healthy premenopausal women achieved significant improvements in HRR60 and following a 3‐month intensive lifestyle intervention.     

The Application of the Yo‐Yo Intermittent Endurance Level 2 Test to Elite Female Soccer Populations

The aim of this study was to evaluate the application of the Yo‐Yo intermittent endurance test level 2 (Yo‐Yo IE2) to elite female soccer populations. Elite senior (n = 92), youth (n = 42), domestic (n = 46) and sub‐elite female soccer players (n = 19) carried out the Yo‐Yo IE2 test on numerous occasions across the season. Test–retest coefficient of variation (CV) in Yo‐Yo IE2 test performance in domestic female players was 4.5%. Elite senior female players' Yo‐Yo IE2 test performances were better (P < 0.01) than elite youth, domestic and sub‐elite players (mean ± standard deviation; 1774 ± 532 vs 1490 ± 447, 1261 ± 449, and 994 ± 373 m). For elite senior female players, wide midfielders (2057 ± 550 m) had a higher Yo‐Yo IE2 test performance (P < 0.05) than central defenders (1588 ± 534 m) and attackers (1516 ± 401 m), but not central midfielders (1764 ± 473 m) or full‐backs (1964 ± 522 m). Large correlations were observed between Yo‐Yo IE2 test performance and the total and high‐intensity distance covered (r = 0.55; P < 0.05) during elite senior soccer matches (r = 0.70; P < 0.01). A large correlation was also obtained between Yo‐Yo IE2 test performance and (r = 0.68; P < 0.01). Performances in the Yo‐Yo IE2 test were greater (P < 0.05) in the middle and the end of the season compared with the preparation period for elite youth female players (1767 ± 539 and 1742 ± 503 vs 1564 ± 504 m) and in elite senior female players, Yo‐Yo IE2 test performance increased by 14% (P < 0.01) after completing 4 weeks of intense training prior to the FIFA Women's World Cup Finals (2049 ± 283 vs 1803 ± 342 m). The data demonstrate that the Yo‐Yo IE2 test is reproducible and is an indicator of the match‐specific physical capacity of female soccer players. Furthermore, the Yo‐Yo IE2 test illustrates sensitivity by differentiating intermittent exercise performance of female players in various competitive levels, stages of the season and playing positions.     

Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: A pilot study

This pilot study investigated whether a 10‐week running program (10wkRP), which reduced the oxygen cost of running, affected resultant ground reaction force (GRF), leg axis alignment, joint moment characteristics, and gear ratios. Ten novice, female runners completed a 10wkRP. Running kinematics and kinetics, in addition to oxygen consumption () during steady‐state running, were recorded pre‐ and post‐10wkRP. decreased (8%) from pre‐10wkRP to post‐10wkRP. There was a better alignment of the resultant GRF and leg axis at peak propulsion post‐10wkRP compared with pre‐10wkRP (10.8 ± 4.9 vs 1.6 ± 1.2°), as the resultant GRF vector was applied 7 ± 0.6° (P = 0.008) more horizontally. There were shorter external ankle moment arms (24%) and smaller knee extensor moments (23%) at peak braking post‐10wkRP. The change in was associated with the change in alignment of the resultant GRF and leg axis (r_s = 0.88, P = 0.003). As runners became more economical, they exhibited a more aligned resultant GRF vector and leg axis at peak propulsion. This appears to be a self‐optimization strategy that may improve performance. Additionally, changes to external ankle moment arms indicated beneficial low gear ratios were achieved at the time of peak braking force.     

Peak oxygen uptake and regional oxygenation in response to a 10‐day confinement to normobaric hypoxia

We investigated the effect of hypoxic acclimatization per se, without any concomitant influence of strenuous physical activity on muscle and cerebral oxygenation. Eight healthy male subjects participated in a crossover‐designed study. In random order, they conducted a 10‐day normoxic (CON) and a 10‐day hypoxic (EXP) confinement. Pre and post both CON and EXP confinements, subjects conducted two incremental‐load cycling exercises to exhaustion; one under normoxic, and the other under hypoxic (F_IO₂ = 0.154) conditions. Oxygen uptake (), ventilation (), and relative changes in regional hemoglobin oxygenation (Δ([HbO₂]) in the cerebral cortex and in the serratus anterior (SA) and vastus lateralis (VL) muscles were measured. No changes were observed in the CON confinement. Peak work rate and were similar pre and post in the EXP confinement, whereas increased in the EXP post normoxic and hypoxic trials (P < 0.05). The exercise‐induced drop in VL Δ[HbO₂] was less in the post‐ than pre‐EXP trial by 4.0 ± 0.4 and 4.2 ± 0.6 μM during normoxic and hypoxic exercise, respectively. No major changes were observed in cerebral or SA oxygenation. These results demonstrate that a 10‐day hypoxic exposure without any concomitant physical activity had no effect on normoxic or hypoxic , despite the enhanced VL oxygenation.     

Autonomic recovery following sprint interval exercise

The autonomic nervous activity was assessed following supramaximal exercise through heart rate (HR) and blood pressure (BP) variability (HRV and BPV) and baroreflex sensitivity (BRS). The beat‐to‐beat HR and BP were recorded during the supine and standing states before (PRE) and at 60 (R60) and 120 min (R120) following single (one Wingate, 1W) and multiple sprint intervals (four Wingates interspersed with 4 min of light cycling, 4W). The supine low frequency (LF) component was increased (P<0.001) and the high frequency (HF) was reduced (P<0.01) at R60 (LF, 178.1 ± 11.0; HF, 74.8 ± 10.5) compared with PRE (LF, 140.2 ± 7.4; HF, 110.4 ± 7.2) after both exercises. Supine systolic BPV LF:HF was higher at R60 (4.6 ± 1.4) compared with PRE (6.8 ± 2.4) only after 4W (P=0.035). Supine BRS was lower (P<0.001) at R60 (6.8 ± 1.1) than at PRE (15.3 ± 1.8) and R120 (11.3 ± 1.3). BRS at R120 remained lower after 4W (P=0.02). Standing BRS was less (P<0.001) at R60 (2.3 ± 0.5) than at PRE (5.6 ± 0.8) or R120 (3.7 ± 0.6) and returned to PRE values only after 1W. We concluded that (a) autonomic balance is shifted to a greater sympathetic and less parasympathetic activation following both types of exercise, (b) it takes longer than 1 h to recover following supramaximal exercise and (c) the recovery is longer after 4W than 1W.     

A 4‐week instructed minimalist running transition and gait‐retraining changes plantar pressure and force

The purpose of this study is to compare changes in plantar pressure and force using conventional running shoes (CRS) and minimalist footwear (MFW) pre and post a 4‐week MFW familiarization period. Ten female runners (age: 21 ± 2 years; stature: 165.8 ± 4.5 cm; mass: 55.9 ± 3.2 kg) completed two 11 km/h treadmill runs, 24 hours apart, in both CRS and MFW (pretest). Plantar data were measured using sensory insoles for foot strike patterns, stride frequency, mean maximum force (), mean maximum pressure () and eight mean maximum regional pressures. Subjects then completed a 4‐week familiarization period consisting of running in MFW and simple gait‐retraining, before repeating the tests (posttest). During the pretests, 30% of subjects adopted a forefoot strike in MFW, following familiarization this increased to 80%; no change occurred in CRS. A significant decrease in in both MFW and CRS (P = 0.024) was observed from pre‐post, and a significant decrease in heel pressures in MFW. was higher in MFW throughout testing (P < 0.001).A 4‐week familiarization to MFW resulted in a significant reduction in in both the CRS and MFW conditions, as well as a reduction in heel pressures. Higher was observed throughout testing in the MFW condition.     

Interaction of cardiac and muscle mechanical afferents on baroreflex control of the sinus node during dynamic exercise

The effects of cardiopulmonary baroreceptors and muscle mechanoreceptors stimulation on cardiac baroreflex sensitivity (BRS), and heart rate variability (HRV) were evaluated by measuring continuously and non‐invasively systolic blood pressure (SBP) and pulse interval (PI) during upright and supine passive cycling. BRS and HRV were evaluated with the cross‐correlation method (xBRS) and in the frequency domain, respectively. At rest, the shift from upright to supine posture enhanced xBRS from 16.4±12.1 to 23.4±12.9 ms/mmHg, and the high frequency (HF, 0.15–0.4 Hz) power of HRV from 48.9±18.6 to 55.1±14.7 normalized units (NU), while it attenuated the low‐frequency (LF, 0.04–0.15 Hz) power from 51.1±18.6 to 44.9±14.7 NU (P<0.05), respectively. During both upright and supine passive exercise, xBRS and the HF power were attenuated (10.0±8.0 and 12.5±9.0 ms/mmHg; 41.1±21.2 and 41.5±12.7 NU, respectively; P<0.05) and the LF power increased (58.8±21.2 and 58.5±12.7 NU, P<0.05), compared with rest. The effect of mechanoreflex activation overrides that of the cardiopulmonary baroreceptors loading resulting in decreased cardiac vagal outflow and reduced BRS during supine passive exercise.     

Stimulating whole saliva affects the response of antimicrobial proteins to exercise

This study investigated the salivary secretion rates of antimicrobial proteins in response to prolonged, exhaustive exercise in both stimulated (STIM) and unstimulated (UNSTIM) saliva flow sample methods. Twenty‐four trained men cycled for 2.5 h at 60% and then to exhaustion at 75% . Timed collections of whole saliva were made before exercise, mid‐exercise, at the end of the moderate exercise bout and post‐exhaustive exercise. After each UNSTIM collection, a STIM sample was collected following chewing flavored gum for 1 min. Saliva was analysed for lysozyme, α‐amylase and salivary immunoglobulin A (s‐IgA), and secretion rates were calculated. Saliva flow was 156% higher in STIM compared with UNSTIM (P < 0.001) and decreased with exercise in STIM only (P < 0.001). Exercise increased lysozyme and α‐amylase levels and secretion rates were 144% higher and 152% higher in STIM compared with UNSTIM for lysozyme and α‐amylase, respectively (all P < 0.001). S‐IgA concentration (P < 0.05) and secretion rate (P < 0.001) increased with exercise but were both lower in STIM compared with UNSTIM (P < 0.001). In conclusion, a STIM saliva flow collection during exercise by chewing flavored gum increased the quantity of saliva and the secretion of lysozyme and α‐amylase, but had a limited impact on the secretion of s‐IgA.     

Ice slurry ingestion does not enhance self‐paced intermittent exercise in the heat

This study aimed to determine if ice slurry ingestion improved self‐paced intermittent exercise in the heat. After a familiarisation session, 12 moderately trained males (30.4 ± 3.4 year, 1.8 ± 0.1 cm, 73.5 ± 14.3 kg, O_2max 58.5 ± 8.1 mL/kg/min) completed two separate 31 min self‐paced intermittent protocols on a non‐motorised treadmill in 30.9 ± 0.9 °C, 41.1 ± 4.0% RH. Thirty minutes prior to exercise, participants consumed either 7.5 g/kg ice slurry (0.1 ± 0.1 °C) (ICE) or 7.5 g/kg water (23.4 ± 0.9 °C) (CONTROL). Despite reductions in T_c (ΔT_c: ?0.51 ± 0.3 °C, P < 0.05) and thermal sensation prior to exercise, ICE did not enhance self‐paced intermittent exercise compared to CONTROL. The average speed during the walk (CONTROL: 5.90 ± 1.0 km, ICE: 5.90 ± 1.0 km), jog (CONTROL: 8.89 ± 1.7 km, ICE: 9.11 ± 1.5 km), run (CONTROL: 12.15 ± 1.7 km, ICE: 12.54 ± 1.5 km) and sprint (CONTROL: 17.32 ± 1.3 km, ICE: 17.18 ± 1.4 km) was similar between conditions (P > 0.05). Mean T_sk, T_b, blood lactate, heart rate and RPE were similar between conditions (P > 0.05). The findings suggest that lowering T_c prior to self‐paced intermittent exercise does not translate into an improved performance.     

The effect of ageing and fitness on thermoregulatory response to high-intensity exercise

There are conflicting reports as to whether ageing causes a decreased thermoregulatory response, or if observed differences in previous studies are related to maximal aerobic capacity or training status. This study hypothesized that thermoregulatory response to severe exercise‐heat stress is maintained with ageing when both young and older subjects are well trained. Seven older highly trained (OHT = 51–63 years) cyclists were matched with two groups of young cyclists (19–35 years); one group matched for training status [young highly trained (YHT) participants, n = 7] and another for [young moderately trained (YMT), n = 7]. Each participant exercised at 70% in hot (35°C, 40% relative humidity) and thermoneutral (20°C, 40% relative humidity) conditions for 60 min. Final rectal temperature in the thermoneutral and heat (YHT = 39.13 ± 0.33°C, YMT = 39.11 ± 0.38°C, OHT = 39.11 ± 0.51°C) tests were similar between all three groups. %HR_max (heat test: YHT = 92.5 ± 6.0%, YMT = 91.6 ± 4.4%, OHT = 88.6 ± 5.1%), skin temperature, and cutaneous vascular conductance during cycling in both environments were similar between groups. Lower sweat loss and evaporative heat loss in the heat test in the OHT and YMT groups when compared with the YHT group reflected lower metabolic heat production. The findings of the present study suggest that thermoregulatory response is maintained with age among highly trained subjects.     

A steep ramp test is valid for estimating maximal power and oxygen uptake during a standard ramp test in type 2 diabetes

A short maximal steep ramp test (SRT, 25 W/10 s) has been proposed to guide exercise interventions in type 2 diabetes, but requires validation. This study aims to (a) determine the relationship between W_max and reached during SRT and the standard ramp test (RT); (b) obtain test‐retest reliability; and (c) document electrocardiogram (ECG) abnormalities during SRT. Type 2 diabetes patients (35 men, 26 women) performed a cycle ergometer‐based RT (women 1.2; men 1.8 W/6 s) and SRT on separate days. A random subgroup (n = 42) repeated the SRT. ECG, heart rate, and were monitored. W_max during RT: 193 ± 63 (men) and 106 ± 33 W (women). W_max during SRT: 193 ± 63 (men) and 188 ± 55 W (women). The relationship between RT and SRT was described by men RT (mL/min) = 152 + 7.67 × W_max SRT1 (r: 0.859); women RT (mL/min) = 603 + 4.75 × W_max SRT1 (r: 0.771); intraclass correlation coefficients between first (SRT1) and second SRT W_max (SRT2) were men 0.951 [95% confidence interval (CI) 0.899–0.977] and women 0.908 (95% CI 0.727–0.971). No adverse events were noted during any of the exercise tests. This validation study indicates that the SRT is a low‐risk, accurate, and reliable test to estimate maximal aerobic capacity during the RT to design exercise interventions in type 2 diabetes patients.     

Impact of single and multiple sets of resistance exercise in type 1 diabetes

To examine glycemic and glucoregulatory responses to resistance exercise (RE) sessions of different volume in type 1 diabetes (T1DM). Eight T1DM (seven males: one female; age: 38 ± 6 years, HbA_1C: 8.7 ± 1.0%/71 ± 11 mmol/mol) attended the research facility fasted and on four separate occasions, having taken their usual basal insulin, but omitted morning rapid‐acting insulin. Participants completed a 1SET (14 min), 2SET (28 min), 3SET (42 min) RE session (eight exercises × 10 repetitions) at 67 ± 3% one‐repetition‐maximum followed by 60‐min recovery, or a resting trial (CON). Venous blood samples were taken before and after exercise. Data (mean ± SEM) were analyzed using repeated‐measures analysis of variance (P ≤ 0.05). RE did not induce hypoglycemia (BG < 4 mmol/L). During recovery, blood glucose (BG) concentrations remained above pre‐exercise after 1SET (15–60 min, P < 0.05) and 2SET (0–60 min, P < 0.05) but comparable (P > 0.05) with pre‐exercise after 3SET. BG_{IAUC(area‐under‐curve)} (mmol/L/60 min) was greater after 1SET and 2SET vs CON (1SET 103.6 ± 36.9 and 2SET 128.7 ± 26.1 vs CON ?24.3 ± 15.2, P < 0.05), but similar between 3SET and CON (3SET 40.7 ± 59.3, P > 0.05). Under all trials, plasma creatine kinase levels at 24 h post‐exercise were similar (P > 0.05) to pre‐exercise. RE does not induce acute hypoglycemia or damage muscle. BG progressively rose after one and two sets of RE. However, inclusion of a third set attenuated exercise‐induced hyperglycemia and returned BG to that of a non‐exercise trial.     

Oxygen uptake plateau occurrence depends on oxygen kinetics and oxygen deficit accumulation

We tested the hypothesis that participants with an oxygen uptake () plateau during incremental exercise exhibit a lower VO₂‐deficit (VO_2DEF)‐accumulation in the submaximal intensity domain due to faster ramp and square wave O₂‐kinetics. Twenty‐six male participants performed a standard ramp test (increment: 30 W·min^?1), a ramp test with an individualized ramp slope and a two‐step (moderate and severe) square wave exercise followed by a ‐verification bout. VO_2DEF was calculated by the difference between individualized ramp test O₂ and O₂‐demand estimated from steady‐state O₂‐kinetics. Twenty‐four participants verified their O_2max in the verification test. Ten of them showed a plateau in the individualized ramp test. VO_2DEF at the end of this ramp test (4.34 ± 0.60 vs 4.54 ± 0.43 L) was not different between the plateau and the non‐plateau group (P > 0.05). The plateau group had a significantly (P < 0.05) lower VO_2DEF 2 minutes before termination of the individualized ramp test (2.24 ± 0.40 vs 2.78 ± 0.33 L). This coincided with a shorter mean response time (43 ± 9 vs 53 ± 7 seconds), a higher increase in O₂ per W (10.1 ± 0.2 vs 9.2 ± 0.5 mL·min^?1·W^?1) at the individualized ramp test as well as shorter time constants of moderate (36 ± 6 vs 48 ± 7 seconds) and severe (62 ± 9 vs 86 ± 10 seconds) square wave kinetics (all P < 0.05). We conclude that the O₂‐plateau occurrence requires a fast O₂‐kinetics and a low VO_2DEF‐accumulation at intensities below O_2max.     

Relationship between changes in pulmonary kinetics and autonomic regulation of blood flow

Various regulatory mechanisms of pulmonary oxygen uptake () kinetics have been postulated. The purpose of this study was to investigate the relationship between vagal withdrawal, measured using RMSSDRR, the root mean square of successive differences in cardiac interval (RR) kinetics, a mediator of oxygen delivery, and kinetics. Forty‐nine healthy adults (23 ± 3 years; 72 ± 13 kg; 1.80 ± 0.08 m) performed multiple repeat transitions to moderate‐ and heavy‐intensity exercise. Electrocardiography, impedance cardiography, and pulmonary gas exchange parameters were measured throughout; time domain measures of heart rate variability were subsequently derived. The parameters describing the dynamic response of , cardiac output () and RMSSDRR were determined using a mono‐exponential model. During heavy‐intensity exercise, the phase II τ of was significantly correlated with the τ of RR (r = 0.36, P < 0.05), Q (r = 0.67, P < 0.05), and RMSSDRR (r = 0.38, P < 0.05). The τ describing the rise in Q explained 47% of the variation in τ, with 30% of the rate of this rise in Q explained by the τ of RR and RMSSDRR. No relationship was evident between kinetics and those of Q, RR, or RMSSDRR during moderate exercise. Vagal withdrawal kinetics support the concept of a centrally mediated oxygen delivery limitation partly regulating kinetics during heavy‐, but not moderate‐, intensity exercise.     

Faster pulmonary oxygen uptake kinetics in children vs adults due to enhancements in oxygen delivery and extraction

This study aimed to examine if the faster pulmonary oxygen uptake (VO_2p) phase 2 in children could be explained by increased O ₂ availability or extraction at the muscle level. For that purpose, O ₂ availability and extraction were assessed using deoxyhemoglobin (HHb) estimated by near‐infrared spectroscopy during moderate‐intensity constant load cycling exercise in children and young adults. Eleven prepubertal boys and 12 men volunteered to participate in the study. They performed one maximal graded exercise to determine the power associated with the gas exchange threshold (GET) and four constant load exercises at 90% of GET. VO_2p and HHb were continuously monitored. VO_2p, HHb, and estimated capillary blood flow () kinetics were modelled after a time delay and characterized by the time to achieve 63% of the amplitude (τ) and by mean response time (MRT: time delay + τ), respectively. Mean values of τ for VO_2p (P < 0.001), of MRT for HHb (P < 0.01) and of MRT for (P < 0.001) were significantly shorter in children. Faster VO_2p kinetics have been shown in children; these appear due to both faster O ₂ extraction and delivery kinetics as indicated by faster HHb and kinetics, respectively.     

Glucose response to exercise in the post‐prandial period is independent of exercise intensity

This study investigated the acute glucose response to low‐intensity, moderate‐intensity, and high‐intensity interval exercise compared to no‐exercise in healthy insufficiently active males using a four‐arm, randomized, crossover design. Ten males (age: 37.3 ± 7.3 years, BMI : 29.3 ± 6.5 kg·m⁻²) completed four 30‐minute interventions at weekly intervals comprising low‐intensity exercise (LIE ) at ~35% O₂R, moderate‐intensity exercise (MIE ) at ~50% O₂R, high‐intensity interval exercise (HIIE ) at ~80% O₂R, and a no‐exercise control. Participants performed cycle ergometer exercise 30 minutes after finishing breakfast. Glucose response was assessed using a continuous glucose monitor under free‐living conditions with dietary intake replicated. A significant effect for intensity on energy expenditure was identified (P  < .001) with similar energy cost in MIE (mean ± SD : 869 ± 148 kJ) and HIIE (806 ± 145 kJ ), which were both greater than LIE (633 ± 129 kJ). The pattern of glucose response between the interventions over time was different (P  = .02). Glucose was lower 25 minutes into each of the HIIE , MIE and LIE trials respectively (mean difference ± SD : −0.7 ± 1.1; −0.9 ± 1.1; −0.6 ± 0.9 mmol·L⁻¹; P  < .05) than in the no‐exercise trial. Glucose response was not different between exercise intensities (P  > .05). Twenty‐four‐hour AUC was not affected by exercise intensity (P  = .75). There was a significant effect for exercise enjoyment (P  = .02), with LIE (69 ± 4) preferred less than HIIE (mean ± SD : 84 ± 14; P  = .02), MIE (73 ± 5; P  = .03), and no‐exercise (75 ± 4; P  = .03). Exercise at any intensity 30 minutes after a meal affects glycemic regulation equally in insufficiently active males. Moderate to vigorous exercise intensities were preferred, and therefore, the exercise guidelines appear appropriate for the prevention of cardiometabolic disease.     

Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice slurry ingestion

The purpose of this study was to compare the effects of a cooling strategy designed to predominately lower thermal state with a strategy designed to lower thermal sensation on endurance running performance and physiology in the heat. Eleven moderately trained male runners completed familiarization and three randomized, crossover 5‐km running time trials on a non‐motorized treadmill in hot conditions (33 °C). The trials included ice slurry ingestion before exercise (ICE), menthol mouth rinse during exercise (MEN), and no intervention (CON). Running performance was significantly improved with MEN (25.3 ± 3.5 min; P = 0.01), but not ICE (26.3 ± 3.2 min; P = 0.45) when compared with CON (26.0 ± 3.4 min). Rectal temperature was significantly decreased with ICE (by 0.3 ± 0.2 °C; P < 0.01), which persisted for 2 km of the run and MEN significantly decreased perceived thermal sensation (between 4 and 5 km) and ventilation (between 1 and 2 km) during the time trial. End‐exercise blood prolactin concentration was elevated with MEN compared with CON (by 25.1 ± 24.4 ng/mL; P = 0.02). The data demonstrate that a change in the perception of thermal sensation during exercise from menthol mouth rinse was associated with improved endurance running performance in the heat. Ice slurry ingestion reduced core temperature but did not decrease thermal sensation during exercise or improve running performance.